The ultimate aim of an electrical connector is to generate an electrical connection capable of enduring the stresses of the service environment. The expected life of an electrical connector in a consumer electronic device varies with the application but generally ranges from 10 to 20 years; the life expectancy of power connector in overhead and underground power lines is usually 30-40 years. In the latter applications, there are stresses on electrical connections stemming from the local environment that may vary from desert-like to very cold, and from dry to damp marine conditions. For any connector type, there are additional stresses that include rapidly-varying conductor temperatures stemming from variations and fluctuations in current loadings, fretting and galvanic corrosion within the connector, mechanical vibrations etc. These stresses are described in detail elsewhere [1-3] and are responsible for electrical degradation of the connections because they generally lead to loss of the mechanical load in electrical interfaces. Maintaining a sufficiently large mechanical contact load in an electrical contact is the major requisite to maintaining reliability in an electrical connector. The major reason for this requisite is addressed below.
The primary criterion for a reliable electrical connection is a sufficiently low electrical contact resistance between the attached conductors and the connector. For connectors that are attached mechanically to wire or cable conductors, such as bolted, pin-in-socket, insulation-displacement connectors (IDCs), compression or wedge connectors, low contact resistance necessitates the application of a sufficiently large mechanical contact force between the connector and the conductors. Furthermore, this contact force must be maintained during the service life of the connector to preclude contact degradation. Compression connectors are particularly susceptible to loss of mechanical contact load. Compression connectors are mechanically squeezed over conductors. Another version of compression connectors relies on the pressure generated by a screw or bolt driven into direct contact with the wire or conductor strands to produce electrical contact between the conductor and a metal barrel. Neither type of compression connector is specifically designed to maintain a selected contact load at electrical interfaces with conductors during service. This contrasts with bolted, pin-type separable connectors, IDCs and wedge connectors where the contact load is maintained through release of elastic energy stored in spring inserts such as Belleville washers and similar components.